1. Field of the Invention
The present invention relates to a wireless communication system for vehicles such as keyless entry system for remotely controlling an electric device mounted on the vehicle such as door locking/unlocking device and power window actuator, by checking on an ID code without using a key.
2. Description of the Related Art
In a related art, a wireless communication system for vehicles for remotely controlling an electric device mounted on the vehicle by checking on an ID code is disclosed in Japanese unexamined Patent publication JP-A-10-131569. The disclosure of the publication will be briefly described herein below.
As shown in FIGS. 5 and 6, operating switches (a door locking switch 1a and a door unlocking switch 1b), a transmission circuit 2a, an ID code memory 2b, and an antenna 2c are provided at a grip section of a portable key 1. When either of the operating switches 1a and 1b is turned on, the transmission circuit 2a reads an ID code from the ID code memory 2b. While a function code (which is set in association with the function of the switch which has been turned on) is added to the ID code, the ID code with the function code is transmitted as a radio wave from the antenna 2c to a receiver (not shown) mounted on a vehicle. Upon receipt of the ID code and the function code, the receiver performs locking or unlocking of a door or actuates a power window function to move a glass window up or down.
That is, when either of the operating switches 1a and 1b of the portable key 1is turned on, locking or unlocking of a door is performed by a reception circuit fixedly provided on the vehicle, in accordance with the function of the switch.
When an operation on either of the operating switches 1a and 1b within a predetermined time after locking or unlocking the door manually is performed, it is judged to be a request for locking or unlocking the door. When the operation continues for a time in excess of the predetermined time, it is judged to be a request for moving up or down a glass window using the power window function. In the condition that the door is in an unlocked state only within the predetermined time after the door is unlocked, the glass window is moved down by the power window function, and in the condition that the door is in a locked state only within the predetermined time after the door is locked, the window glass is moved up by the power window function.
The device, however, has given a sense of inconvenience because the portable key 1 is provided with the operating switches 1a and 1b so that either of the operating keys 1a and 1b must be externally operated with a finger tip or the like to be turned on.
Under such circumstances, recently, there have been made proposals for keys without the operating switches 1a and 1b which keys are so-called electronic keys and devices which are generally called passive keyless entry devices (also called smart keyless entry devices). In these proposals, an ID code is periodically transmitted from a portable key to a receiver without any switch operation, so that the receiver automatically checks the ID code in order to judge whether the key is valid or invalid.
Since this arrangement allows a door to be automatically locked and unlocked without need for the driver to operate a key, the driver's both hands becomes free so that the driver can do various things freely without touching the door or the key.
Such passive keyless entry device may be provided with the power window function. In this case, for example, arrangement may be conceived such that the power window function is enabled for a predetermined time after the driver pulls out the key from an ignition key cylinder to get off the vehicle. How to set the predetermined time to enable the power window function, however, becomes a problem in this case.
For example, the driver becomes free to do some work with a door open for the predetermined time. Therefore, when the driver leaves the vehicle immediately after opening the door with the predetermined time set, for example, at 30 seconds, the state in which the glass window is left open continues for 30 seconds. It cannot be said that this state is preferable for security, in general.
On the other hand, when assumed that the driver gets off the vehicle after doing some work on the seat for about 30 seconds after removing the key, and thereafter attempts to actuate the power window function to put things on the rear seat in order with the door and the glass window left open. In this case, the power window function cannot be actuated, so that it has been necessary to repeat the operation of inserting the key into the ignition key cylinder again to turn on the ignition switch.
A possible solution to the problem may be a system in which an ID code is checked after a press on a power window switch is detected and the power window function is enabled when the check provides a positive result. The check, however, involves a certain amount of time so that timeliness is spoiled due to occurrence of a time loss before the power window is actuated. This may make the driver impatient and result in problems such as damage to salability.